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Old 05-12-2006, 02:32 PM
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Some B&M 250 questions, JimDavis maybe?

Hi all,
I have some questions about the B&m 250 blower (now Weiand 250).
I am trying to piece together a roots blower set-up for a small block mopar. By the time I will do it, I plan to have Magnum heads (drilled for LA intake pattern). I never plan on racing, and I always plan on running pump gas, in Southern California. The vehicle will be an A-100 van, 727 tranny, 3.55 gears with 28 inch tires. The weight of the vehicle will be around 3800-4000 lbs. The vehicle will be semi-daily driven.

I want to first try the setup on a low compression (around 8:1) 318, with a mild cam. After working out the kinks, I might change the long block to a 360 or a 340.

The reasons I was thinking of a 250 sized blower are:

Good compromise for smaller engine sizes, with possibility of using it on a slightly larger engine with low boost (definitely never more than 8 PSI).

Smaller physical size than 6-71

Looks a little similar to a GMC 71 series blower.

Uses 2" 8mm pitch Gilmer belts (less belt throwing as compared to 1/2" pitch, plus slightly more nostalgic look than poly v-belt).

Straight lobe rotor might be more suitable for using with my inteneded manifold - bottom part of tunnel ram, with fabricated adapter plate.

Flexibilty for using either single 4bbl or dual 4 bbl carbs.



Now, I am aware that the Blower Shop makes billet 250 (and 192) blowers. However, right now they are out of my price range. I did notice that they sell parts for the B&M 250 blowers.
I sent them a similar e-mail to this one, but never got a reply. Yes, I'm aware that they see this as just someone waisting their time, so I'm not complaining about it.
I'm also aware that DLI used to offer kits for Mopars. I'm not interested in buying a kit, I'm interested on trying to build my own.



Now (finally) for my questions:

1. Do you know if anyone performs rebuilding services for the B&M 250 blowers?

2. Are there quality problems with those blowers (I heard that the smaller 144/174 blowers have mild steel shafts, and no one wants to rebuild them)?

3. Do you know if the Blower Shop 250 blowers are a somewhat compatible higher quality improved version of the B&M 250? Meaning, do parts interchange? I'm asking becasue as time goes by, I might want to switch to the better Blower Shop case.

4. Does anyone know if Holley/Weiand are actually still making the 250 blower? I know you can theoretically buy one through summit, but the supply time is at least a month, leading me to belive they are not really offering it.

I have also searched this site and the net for info about these blowers, and have not come up with specific answers to these questions.

Thanks a lot for any help,
Ran

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Old 05-12-2006, 05:58 PM
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Quote:
Originally Posted by kick_the_reverb
Hi all,
I have some questions about the B&m 250 blower (now Weiand 250).
I am trying to piece together a roots blower set-up for a small block mopar. By the time I will do it, I plan to have Magnum heads (drilled for LA intake pattern). I never plan on racing, and I always plan on running pump gas, in Southern California. The vehicle will be an A-100 van, 727 tranny, 3.55 gears with 28 inch tires. The weight of the vehicle will be around 3800-4000 lbs. The vehicle will be semi-daily driven.

I want to first try the setup on a low compression (around 8:1) 318, with a mild cam. After working out the kinks, I might change the long block to a 360 or a 340.

The reasons I was thinking of a 250 sized blower are:

Good compromise for smaller engine sizes, with possibility of using it on a slightly larger engine with low boost (definitely never more than 8 PSI).

Smaller physical size than 6-71

Looks a little similar to a GMC 71 series blower.

Uses 2" 8mm pitch Gilmer belts (less belt throwing as compared to 1/2" pitch, plus slightly more nostalgic look than poly v-belt).

Straight lobe rotor might be more suitable for using with my inteneded manifold - bottom part of tunnel ram, with fabricated adapter plate.

Flexibilty for using either single 4bbl or dual 4 bbl carbs.



Now, I am aware that the Blower Shop makes billet 250 (and 192) blowers. However, right now they are out of my price range. I did notice that they sell parts for the B&M 250 blowers.
I sent them a similar e-mail to this one, but never got a reply. Yes, I'm aware that they see this as just someone waisting their time, so I'm not complaining about it.
I'm also aware that DLI used to offer kits for Mopars. I'm not interested in buying a kit, I'm interested on trying to build my own.



Now (finally) for my questions:

1. Do you know if anyone performs rebuilding services for the B&M 250 blowers?

2. Are there quality problems with those blowers (I heard that the smaller 144/174 blowers have mild steel shafts, and no one wants to rebuild them)?

3. Do you know if the Blower Shop 250 blowers are a somewhat compatible higher quality improved version of the B&M 250? Meaning, do parts interchange? I'm asking becasue as time goes by, I might want to switch to the better Blower Shop case.

4. Does anyone know if Holley/Weiand are actually still making the 250 blower? I know you can theoretically buy one through summit, but the supply time is at least a month, leading me to belive they are not really offering it.

I have also searched this site and the net for info about these blowers, and have not come up with specific answers to these questions.

Thanks a lot for any help,
Ran
Well, I am very partial to the 250. I have two of them, one on a '32 roadster and one on a '33 coupe. Both SB Chevys.

I don't know if Holley/Weiand is still making them. I think so but Holley has a great many issues currently and I suspect blowers might be pretty far down on the list. My understanding is that The Blower Shop will rebuild B&M 250 blowers. I have looked at their billet unit....very nice piece....but it's been a couple of years ago and I am not sure if any of the parts are interchangeable with the B&M 250.

I don't know of any quality problems with the blowers. Of course, the limit of my experience is when were building them at B&M. I presume that Holley has continued to use essentially the same materials and manufacturing processes but I don't know that for a fact.

The blower kits that Dick Landy was offering, at least when I was still at B&M, basically adapted one of the smaller B&M blowers (144, 162, 174) to a modified single 4-bbl manifold for Mopar engines. I don't think they ever adapted a 250. The outlet port on the smaller blowers lent themselves to adapting to a four barrel manifold. Doing the same thing with a 250 is going to be more of a challenge because the outlet port (actually ports since there is a divider in the middle) is quite long. You wouldn't be able to adapt it to single 4-bbl manifold. Adapting it to the bottom part of a tunnel ram should work.

The straight rotors versus helix rotors can involve a very lengthy discussion but bottom line is that in all of the tests we did at B&M there wasn't any significant difference. The main advantage of straight two lobe rotors compared to the three lobe helix is that the two lobes take up less space inside the blower housing so each blower revolution actually moves a higher volume of air, all other things being equal. This would assume both blower housings were the same size.

If you have a low enough c.r. you can run as much as 12 pounds of boost with a 250. I am running about 12 on my '33 coupe with a c.r. of 7.6:1. The 350 engine has Dart iron heads and a very mild street cam and made 510 hp on the dyno. However, it has awesome bottom end torque. I can't remember the exact numbers now but it was something like 375 lb. ft. at 2,200 rpm.

At B&M we did hundreds of hours of dyno testing at Dick Landy's with every combination known to man. I definitely am convinced that the way to go is a low c.r. and high boost. There is much less danger of detonation with that combination and it also seems to really boost the bottom end torque. That's because with the higher boost you are spinning the blower faster which really helps at the lower end. Admittedly it can hurt at the high end because high blower speeds heat up the air and lower the efficiency. But if your vehicle is mainly a street driven car, I would rather have the super bottom end performance and maybe sacrifice above 5,500 since I would rarely have it that fast anyway.
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Old 05-12-2006, 08:23 PM
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I too like the B&M 250 series blower. I have one on my 454 in my boat with a Super Chiller Intercooler. I am very happy with this set up. I spoke with a rep from the Blower Shop 2 years ago at PRI with many of the same questions as you. Here is what I was told.

They will rebuild the B&M blowers.

The components will not interchange between their blower and the B&M except for the bearings and I believe, seals.

Since the cases and end plates are made from billet they are stronger and less prone to distortion and flexing.

Holley still offers a blower rebuild service. I am sending mine to them to freshen up shortly. Here is the phone number.

1-800-465-5395 EXT 739 Holley Supercharger rebuilding.

I hope this helps.
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Old 05-15-2006, 08:32 AM
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Thanks a lot Jim and TopFuel, I appreciate the replies...I had a feeling I'd get a straight answer here.
Jim, my concern about the straight versus helix were in regards to distribution with helix type of rotors - I heard that they tend to distribute the mixture more towards the front, so if I used the bottom part of a tunnel ram, I'd have to fabricate a 2-3" deep plenum to sit on top of it and mount the blower to that...a little more complicated than just making a thick aluminum plate that bolts to the tunnel ram bottom. Since the 250 has straight lobes, that's not an issue (I hope).
Regarding DLI - I have an old catalog of his that shows a 250 on a Mopar small block and on a Mopar big block. The only thing about all those "kit-sellers" is that they tend to charge an arm an a leg for non chevy applications (mainly for the intake manifold). It's their right, but I don't see myself paying $800 for a two piece intake manifold.

Good to hear about rebuilding services available, because a used blower is not something most of us average Joes can test at the swap meet and be sure it's good. I looked at getting just a case assembly and nose from Holley, but the price is more than a kit for an SBC, almost worth it to buy a kit, then try to sell the SBC manifold, if going with an all new blower.

Thanks again, now the hunt can begin...

Ran
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Old 05-15-2006, 09:34 AM
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DLI must have developed those 250 kits after I left B&M which was in 1991. I think your theories regarding the straight lobe versus the helix and your particular application are probably accurate. Although keep in mind that the differences in air flow between the two designs is probably insignificant at the speeds at which your engine will be running 99% of the time. A book could be written on the pros and cons of these two designs but the bottom line is in actual performance on a primarily street driven machine, there probably isn't enough difference to ever be concerned about.

Regarding the other post stating the the Blower Shop billet blower has stronger front and rear covers because they are billet, while that statement is no doubt true, the reality is that the covers on the B&M are more than strong enough. The rear cover has almost no load on it and the flat plate casting on the B&M carries the load just as well as a billet plate. The front cover of the B&M is a die casting and they way it is designed, it is just as rigid in that application as a billet cover would be. So, yes, the billet pieces are no doubt stronger but there is no need for them to be.

In all of the thousands of B&M blowers we sold I never heard of any failures due to lack of strength of these particular parts. The only time I ever ran into an issue, and this would be equally true of a billet piece, was on the Boyce Asquith "World's Fastest Street Rod" that we were involved with. This car is one of the "75 Most Significant 1932 Fords" selected by a panel picked by Ford Motor Compny to celebrate the 75th anniversary of the duece next year.

Anyway, this car was running a B&M Megablower, which as a point of interest, is technically the size of a 7-71 GMC blower if there was such a thing. It is halfway between a 6-71 and an 8-71 blower with respect to swept volume. Anyway, the engine in the car was a 497 cid big block making 1,100 hp on pump gas. The problem we always had with the car was the the owner, Boyce Asquith, loved to rev the engine. I could hear from the way the car sounded going down the track that he was over revving it in each gear which I felt was significantly affecting the performance. Even so, the car did run an 8.60-159 which, at the time, was as quick and as fast as any truly driven street rod had ever run.

But after about two runs we would see that the rotors were hitting each other and we would have to replace the blower. After several outings with the car and replacing the blower after every two or three runs we realized that the blower was getting so hot that the aluminum was expanding to the point that the gears were seperating allowing the rotors to fall out of time and start to hit each other. We solved this problem by putting a steel insert into the front case that supported the two bearings. Steel expands at roughly half the rate of aluminum.

However, all of this would have been totally unnecessary if Boyce had kept the engine revs at the ideal (based on dyno runs) of about 7,500. Boyce swore he was shifting at 7,500 but based on the sound of the car going down the track, I didn't think that was the case. So we got an AutoMeter tattle tale tach and after a run we replayed the run on the tach in the pits and he was actually shifting it at about 9,400. What kept a 496 inch big block together at 9,400 is a testament to the engine builder, Dave Zeuschel, but it was obvious that those extreme speeds with the blower drive we were running was turning the blower at speeds it was never designed to see and as a result generating tremendous heat which was the cause of the excessive expansion.

Anyway, I know none of this relates to your issue but I thought it was an interesting piece of history on one of the nation's most significant 1932 Fords. An all steel original car by the way.

Boyce suffered an untimely death due to stomach cancer shortly after this and as a result, the true capabilties of the car were never realized as it never did make a full quarter pass under optimum conditions.
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Old 05-15-2006, 10:12 AM
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Thanks for the added info Jim, and I appreciate the slight off-topic info, it's always interesting to hear stories like that...9,400 rpm, no wonder the blower was overheating! Sheesh...

Ran
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Old 05-15-2006, 10:26 AM
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Just a slight miscalculation of 2,000 rpm. *lol*

I always wondered what the car would have run if it had been shifted at the correct speed. As soon as he went by the power peak of 7,000 rpm the power starts dropping off. Standard procedure is to rev about 10% over the power peak. This typically puts you at the torque peak in the next gear. So technically the car should have been shifted at about 7,700 rpm. I think I had done the calculations with the gearing and looking at the dyno chart and came up with the 7,500 shift point for optimum performance. By going to 9,400 the engine power had to be falling off dramatically and seriously hurting the performance. It had a three speed TH400 in it and he was over-revving both first and second so there were two chances where the performance could have been improved if he had shifted it at 7,500. I suspect the car would have run maybe a couple of tenths better and maybe two or three mph faster. Hard to say. We'll never know. The car has a different milder engine in it now.

Jim
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